This R35 proposal represents a comprehensive, long-term program that explores new mechanisms and therapeutic concepts related to the formation of the unique types of atherosclerotic plaques that cause acute cardiovascular disease (CVD). The training and mentoring of young scientists is also a key part of this program. The PI has held multiple NIH grants without interruption for many years, publishes on atherosclerosis and cardiometabolic disease in the highest impact journals, and has a highly successful record of training young scientists to be independent academic researchers. The program will explore new, highly interrelated concepts related to four key areas in which major gaps exist: (i) inflammation resolution and efferocytosis (clearance of dead cells); (ii) pathophysiology of the minority of atherosclerotic lesions that are most clinically important; (iii) amino acid metabolism in M?s as it relates to high-burden efferocytosis; and (iv) aging-related clonal hematopoiesis (CH). Processes that impair inflammation resolution, which are distinct from those that promote inflammation per se, and defective efferocytosis promote the formation of clinically relevant necrotic, thin-capped plaques. The lab's new work indicates that (i) the ability of M?s to internalize multiple apoptotic cells (high-burden efferocytosis) is critical to avoid necrotic plaques (Cell 2017); and (ii) a pathway related to M? metabolism of apoptotic cell-derived amino acids is critical for high-burden efferocytosis. Another exciting new concept supported by preliminary data is that impaired efferocytosis and resolution are exacerbated by CH, which is emerging as a major age-related risk factor for atherosclerotic CVD. The overall vision of the program is to study these new areas by first using (i) mouse and human M?s to elucidate in-depth mechanisms; and (ii) genetically altered mice to test causation in advanced plaque progression. The R35 will also explore the therapeutic potential of these ideas in pre-clinical models, with the hypothesis that resolution mediator therapy will have efficacy and safety advantages over conventional anti-inflammatory therapy. The PI will then use the flexibility and continuity of the R35 program to move into new directions related to human studies. Through a rich network of collaborators at Columbia and elsewhere?including Columbia's Cardiovascular and Metabolic Precision Medicine program? the program will apply the new discoveries to (i) analyses of human atheroma; (ii) human genetics, including subjects with KOs of genes in resolution/efferocytosis pathways through a collaboration with the PROMIS study; and (iii) studies with human monocyte- and iPSC-derived M?s that are amenable to CRISPR/Cas9-mediated genetic engineering, as guided by the program's mechanistic and human genetic data. Through the flexibility and forward-looking nature of the R35 program, the combination of the proposed mechanistic work and human studies will provide a power combination to fill in critical gaps in how dangerous plaque form; to devise novel therapeutic strategies; and to train and mentor young scientists in this critical area of research. 1